Viana is wanted by a group of Premier League clubs, according to talkSPORT.
Leeds are understood to be furthest along the line and considering a bid of between £8m and £10m.
Leicester have reportedly sent scouts to watch him too, but the departure of their head of recruitment Eduardo Macia is leaving them in limbo.
The other Premier League clubs reportedly interested in Viana, 24, are Watford and Wolves.
Wolves, should they make a move, may well have the upper hand considering their connection to Portuguese football via super agent Jorge Mendes.
Viana has helped Braga average only one goal conceded per game in the Primeira Liga this season, which has kept them within touching distance of Sporting.
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